Slide rule



Patented Dec. 7, 1926.

'UNITED STATES PATENT OFFICE.

FREDERICK A. SHERRER, OF EASTON. IENNSY1.|VANIA, AND VICTOR F. HESS,l OF ORANGE, NEW JERSEY, ASSIGNORS TO UNITED STATES RADIUM CORPORATION, A

CORPORATION OF NEW YORK.

SLIDE RULE.

Application filed April 11, 1922.V Serial No. 551.590.

traverse media having different powers of,

absorbing them.

The invention is directed to the provision of an instrument which will assist the sur-- geon or operator, in the treatment of diseased tissues by means of radio-active material, to calculate rapidly andapproximately the intensity of the gamma ray radiation at an distance within the tissues being treat when the applicator is placed at varying distances above the surface of the skin and also When applicators of different strengths and different configuration are emloyed. Another purpose of the invention 1s to enable the operator to make such estimates rapidly and conveniently' with applicators in conjunction with filters of dii'erent materials and different thicknesses.

Conversely stated, the special purpose of the invention is to enable the operator, in the treatment of tissues with gamma rays to determine quickly the distance above the skin at which a given applicator of known power should be placed in order to secure a pre-determined intensity of radiation at any depth within the sound or diseased tissue, whether the diseased tissue is located at or below the surface of the skin, and in the latter instance, independently of the distance of the diseased tissue below the. surface of the skin.

In the treatment of diseased tissues by means of gamma rays from radio-active material, vsuch as a radium salt or radium emanation, in closed tubes or applicators, the amount of exposure or dosage which the sound tissue will stand without causing erythema and also the amount of exposure to which 'the diseased ltissue should be subjected to get the best results must be carefully taken into account. This exposure or dosage is measuredin terms of units of intensity of gamma ray radiation multiplied by the time of exposure. It is, therefore,

necessary that the surgeon or operator in the treatment of tissues with such radiations, should be able to estimate the intensity of gamma ray radiation from any given applicator ot' any given radium content and with any given filter or container and at varying distances from the tissue. Moreover, he must be able to calculate or estimate this intensity at any given depth within either the sound or the diseased tissue, with varying distance of the diseased tissue below the surface of the skin.v

It -Will be readily understood from the foregoing statements that a number of factors which must be taken into account in estimating the dosage or amount of exposure is unusually large and the calculation /is correspondingly complicated. These complications introduce possible sources of error, which, unless carefully guarded against, iutroduce uncertainties in the treatment of tissues by this means which constitue one of the main objections to the method in actual practice.

The present invention aifords means for readily overcoming these uncertainties and for making the method more amenable to control.

As illustrative of the number of factors which must be taken into account and of the intricate type of calculations involved in practical radio-therapy, reference may be made to an example. The applicator may consist of a needle containing 10 mg. of radium in the form of a salt contained in a 1 mm. brass container or filter, the radiations may traverse in succession 1 cm. of air and l cm. of sound tissue before reaching the diseased tissue, and it may be desired to determine the intensity at the surface of the skin and at 'l cm. within the sound tissue and also at 1 cm. ywithin the diseased tissue. The necessary calculations of the intensity at the different points mentioned would ordi' nai-ily be made by first computing the transmitted intensity in accordance with the exlaw of absorptionis more complicated and 'Ico clearly understoo not so well known to those skilled in radiotherapy. Ordinarily this computation is made by means Aof the formula,

in which I 'is the intensity of transmitted radiation, I0 is the intensity of radiation' entering medium, d is the total thickness in cm., f is Bunsens absorption coefcient and depends only upon the nature of the medium. i Y

It will be observed that by this method a separate calculation of complicated character is required for each selected distance in each separate medium and therefore that numerous values must be held in mind'or recorded. The calculation of the transmitted intensity by means of the formula i e 1,1 o-d for any given distance within any selected medium may be carried out by means of an engiiieers logarithmic slide-rule, but this operation, also, is a complicated one and must be repeated and the results carriedin the memory or separately recorded asmany times as there are media traversed by the radiation. previously stated, isobjectionable in actual practice not only because of the well-known fact that men in the medical profession', as a rule, are not familiar with theJ vuse of the engineers logarithmic slide-rule, but also because of the plurality of separate calculations involved' and the necessity of relying upon the memory or upon a plurality of written notations. Another source of uncertainty and'error in making the calculations according to this method is the confusion in the published literature with regard to theunits in which various quantities in the formula are to 'be expressed and further' confusion as to the names ofthe vdifferent quantities themselves.

All the foregoing uncertainties and sources of error in calculating are largely or completely, overcome by means of the present invention, the various novel features and advanta es of which will be more from the following description of the preferred embodiment of my invention.

In the accompanying drawings, Fig. 1 is a plan ofthe indicating device or tabular chart illustrating or embodying one form of our invention, and Fig. 2 is a view of one ct' the slides, and Fig. '3 is a transverse cross-section of the instrument.

A is a slide graduated in units of distance .on the left. hand side thereof and graduated in correspondinfr intensities of gamma ray radiations in ordinaryair on theright ham? side thereof. Slide A also carries appropri This method of calculation, as

'port Vprovided with three ate lettering at the top to indicate that it is to be used to assist in'calculating the intaining 10 mg. of radium `enclosed in a 1 mm. brass filter tube or container The intensity scale a on the right hand side of slide A indicating intensities of gamma. ray -radiation is identified by appropriate lettering immediately above the zero mark. The d stance scale b on the left side of slide A is identified by appropriate lettering in a similar position witlirespect to the z ci'o mark'of the distance scale.

`tensities obtained with a radium needle con- B is a slide carrying two graduated scales c and d. The identifying numerals on scale d indicate the distance in centimeters from Athe skin (within the tissue) and those on scale c indicate the absorption factor for hu.

C in t e particular em odiment illus-` trated in the drawing is al slide carrying a single graduated scale e in which the numbers identifying the2 graduations .are expressed in cm.

The slide B in the example illustrated corresponds to the second medium exclusive of the filter traversed by the radiation andthe two scales carried by this slide B in the drawing may be identified, res ectively, by a legend reading absor tion actor in human tissue alongside t 4e graduated scale c on the left of the slide and by `a legend reading distance from the .skin (within tissue) alongside the scale cl on the right of the slide B.

Scale C corres onds to the third medium exclusive of the lter traversed by the radiation and the single scale e carried by this sli-de C is similarly identified byI the legendr I distance from surface of diseased tissue.

D in the drawing 1s a mounting or supuides or tracks,

E, F, G, for the three sca es A, B, C, re-

spectively, andadapted to hold the scales in proper position relative to each other and adapted also to ermit the slides to be moved relatively `to eac other in such manner that the zero marking of any distance scale may be brought into correspondence with any distance marking on either of the remaining scales.

In the device illustrated in the drawing the mounting or support D consists of a' flattened tube of transparent Celluloid and the slides are stripsof white Celluloid with the graduation marks and identifying numerals and letterin in black ink. The guides `or tracks E, means of two rows of rivets or eyelets ff In operatin uriwing, t e slide B is ordinarily keptgin and Gare formed by the indicating device or l I Y amma ra ta ular chart illustrated in the lao a fixed position and the other two slides A, and C are moved relative to slide B and also relative to each other. The zero mark of the distance scale e on the slide C is to be set opposite the number on the scale l on the right hand side of slide B which corresponds to the distance of the upper surface of the .diseased tissue from the surface of the skin. The slide A, or applicator slide, is raised until the number on the left hand side of thescale corresponding to the 'distance of the applicator above the surface of the skin is opposite the zero mark of the .distance scale d on slide B.

After `setting the slides as indicated above, the intensity of radiation on or in the tissde is read off from the numbers identifying the markings on scale a which lie opposite any selected number on scale d on the right of sli-de B. The absorption factors identifying the graduations-on scale c on the left hand side of slide B are to be Iapplied to tlie corresponding intensity vnumbers identifying the graduations of scale a on the right hand side of slide A after the slides A and C have been set to correspond to the distances of the applicator from the surface of the skin and to the distance of the surface of the diseased tissue below the skin, respectively, as. described above.

The operation'of the indicating device may be further illustrated by means of a specific example as-follows;

If a radium needle applicator containing 1()l mg. of radium with a 1 mm. brass filter (corresponding to the slide A illustrated in the drawing) is placed 1 cm. above the surface of the skin and if further the surface-of the diseased tissue is 2 cm. below the surface of the skin the procedure in operating the device and taking the readings would be as follows: A

Set numeral 1 of the left hand scale b of the slide A (marked Radium Needle 10 mg. filter; 1 mm. Brass) opposite the zero mark of the right hand scale d of' slide B. Set

the. zero mark of the scale e on slide C opposite the numeral 2 of the right hand scale d of slide B. Having thus set the slides for the given set of conditions, Ythe intensities in milll-eves at various points upon and within thesound and diseased tissuel are read ofi as follows:

At the surface of the skin or upper surface of the sound tissue, the intensity of radiation is read off from the number on the graduated scale awhich lies opposite the zero mark of the graduated scale d on the right of the slide B. and is seen' to be 8.97. At 1 cm. below the surface of the skin and within the sound tissue, the intensity is read oti from the number on the scale a which lies opposite the numeral 1 of the scaled and from the corresponding absorptionfactor on scale c and is seen to be 2.3 multiplied by .932214. At the surface of the diseased tissue, the intensity is read ofi1 from the numbers on scales a and c lying o posite the zero mark on scale e on the slide and is .seen to be'1.03 multiplied by .86:0.89 approximately. At 2 cm. below the surface of the diseased tissue and Within. the same, the' intensity is read off from the numbers on lscales a and c lying opposite the numeral 2 of the graduated scale e on the slide- C and is seen to be .371 multiplied by .74:027 approximately.

It will be understood that the invention is not limited to the particular arrangement of slides or-to the particular graduation scales and identifying numbers shown in the drawing, but various other arrangements of slides and different graduated scales and identification numbers may be used Without departing from the scope of'the` invention. These variations and modifications vvill be understood by one skilled in the art of constructing indicating devices of the general type to which the invention belongs. Thus the Values of the graduations on the different graduated scales may be expressed in units otherthan those illustratcd. Also other graduated scales may be added to certain of the slides to correspond to different types of tissue or media. Thus a graduation scale of absorption factors on the right hand sideof the slide C may be added expressing these absorption factors as ratios of the transmitted intensity in the diseased tissue to the corresponding transmitted intensities in the sound tissue at corresponding distances. In this instance, the absorption factors for the diseased tissue would be applied to the intensity values obtained as explainedin the example described above. Also, the absorption factors may be expressed in an inverse. ratio in which instance they would have to be placed on a different slide from the one illustrated in the drawing.

We claim:

1. An adjustable tabular chart comprising a slide having a scale and'also a series of indicated values bearing a"'definite fixed relation with respect to the indications on the scale, a second scale with respect to which the first scale is relatively movable, a second series of indicated values bearing a predetermined fixed relation with respectto` the indications on the second scale, said scales and series of values cooperating so that when the first scale is set to the second scale a result may be obtained byl using the two values identified by a chosen point on the second scale. y

2. An adjustable tabular chart comprising a slide having a scale and also a series of indicated values bearing a predetermined fixed relation with respect to the indications on the scale, a second scale with respect to which the first scale is relatively movable,

a predetermined iixed relation a second series of indicated values bearing with respect to the indications on the second scale, and an additional slide having a scale thereon, all of said scales and seriesi of Values cooperating so that When the scale of the rst named slide is setto the second scale a result may be obtained by usingthe two values videntified by a chosen point on the second scale and so that when said additional slide is set to the second scale a result may be obtained by using the two values identified by a chosen tional slide. c

3. An adjustable tabular chart comprising point on the scale of said addila first strip carrying a distance scale and carrying also a scale of corresponding intensity values, a second strip carrying a like distance scale and a scale of corresponding absorption factor ratios and a third strip carrying a distance scale, the first and third .and after also setting strips being adjustable with respect to each other and also with res ect tothe second strip, the said scales being adapted to cooperate with each other in such manner that after setting the distance scale on the first strip to the distance scale on the second strip 'l In testimony whereof we aliix our signatures.

' FREDERICK A. SHERRER.

VICTOR FRAN CISHESS. 

